1. Field of the Invention
This invention relates to monoazo dyestuff mixtures for polyester fibers. More specifically, it relates to monoazo dyestuff mixtures which dye polyester fibers in yellow colors excellent in various fastness properties, in particular, light fastness, sublimation fastness, washing fastness, perspiration fastness and water fastness, and which are also excellent in heat resistance and alkali discharge printing properties.
2. Description of the Prior Art
Recently, an alkali discharge printing process has been increasingly frequently carried out as a new dyeing process for polyester fibers. The principle of the alkali discharge printing is to hydrolyze a dyestuff with alkali, thereby depriving it of its affinity to polyester fibers.
Therefore, the dyestuffs intended for that purpose contained carboxylate ester groups, hydroxyl groups etc. which had great hydrophilic properties and were easily reactive with alkali in their backbone structure, and for that reason, they had a disadvantage that their wet fastness, such as washing fastness, perspiration fastness, water fastness etc. and also heat resistance were poor.
Heretofore, dyestuffs having similar structures to those of this invention are known from Japanese Patent Publication No. 5456/1978 and Japanese Patent Application Laid-open No. 49661/1982, but it has been desired that their wet fastness and heat resistance be more improved while good alkali discharge printing properties be maintained.
Previously, the present inventors had invented dyestuffs of the general formula [I] below which dye polyester fibers in yellow colors and provide dyed cloths excellent in various fastness properties such as light, sublimation, wet and the like fastness properties and had filed an application for a patent (Japanese Patent Application No. 10229/1983): ##STR3## wherein R.sup.1 represents an alkyl group, a phenoxyalkyl group, an alkoxyalkyl group or an aralkyl group.
However, when used singly, these dyestuffs had been expected to be further improved in an aspect of dyeing characteristics such as dyeing affinity, temperature dependence at the time of dyeing, build-up properties etc. although their various fastness properties such as light, sublimation, wet and the like fastness properties, and alkali discharge printing properties were excellent. A further study has been carried out to improve dyeing characteristics such as dyeing affinity, temperature dependence at the time of dyeing, build-up properties etc. of the yellow monoazo dyestuffs of the above general formula [I], and, as a result, it has also been discovered that mixtures of dyestuffs of the general formulae [II] and [III] hereinbelow at certain mixing ratios are excellent in the above-described dyeing characteristics while maintaining or even improving the above-described advantages, i.e., various fastness properties, heat resistance, alkali discharge printing properties.